The invention relates to a torque limiting coupling, especially in a driveline, for driving agricultural implements or machinery. The coupling includes a coupling hub and a rotatably supported coupling sleeve. Driving members are movably arranged in inwardly directed, circumferentially distributed recesses of the coupling hub. The heads of the driving members, in the torque transmitting position, each engage a corresponding recess in the opposed inner face of the coupling sleeve. The heads, in the switched-off position, are disengaged from the recesses. The rotational axis of the coupling sleeve and coupling hub extends parallel to the torque transmitting face of the heads. The base of the driving elements is provided with two switching faces. One switching face provides support in the torque transmitting position, and the other switching face, provides support in the switched-off position. The switching faces are loaded by respective switching faces of a switching cam. The switching cam is spring-loaded in the direction of the torque transmitting position and movable transversely relative to the respective driving member arranged in the recess in the coupling hub. The switching faces serve torque transmitting purposes and extend at an angle relative to the central axis of the respective driving member. The angle is greater than the angle of the switched off position. Also, the switching faces are designed so as to correspond to one another.
DE-PS 912 411, published Apr. 15, 1954, illustrates a torque limiting coupling. The torque limiting coupling is designed to transmit torque and to be switched off in both possible directions of rotation. For this purpose, the head faces of the driving members are designed as cylindrical members. Each member includes two inclined faces engaging coupling sleeve recesses with corresponding inclined faces. Towards the inside, the driving members are provided with inclined faces loaded by switching cams, which are movable transversely relative to the driving members. The switching cams are each loaded towards one another in the direction of the switching faces of the driving members by a spring. In the disconnected position, the switching cams, with their faces extending parallel to the cylindrical face, are supported on the cylindrical face of the driving members. Re-engagement is possible through actuation from the outside. For this purpose, there is provided a switching ring which, via a slot control system, engages the driving members and moves them back into the torque transmitting position. With such a design, the driving members, when torque is transmitted, carry out a tilting movement around all axis extending through the central axis of the driving members and parallel to the rotational axis of the torque limiting coupling. As the spring forces exerted by the switching cams cancel one another, these cannot make a stabilizing contribution.
The tilting movement leads to edge pressure between the recess edges loaded by the respective driving members in the torque transmitting direction towards the outer face of the coupling hub. This leads to an increase in the size of the recess through wear and to wear on the driving members.
In addition, there is built up a projection which increases the friction between the outer face of the coupling hub and the inner face of the coupling sleeve. The overall result is that the reaction accuracy is reduced and furthermore, increasing wear may lead to overloading.